/Engine/Source/Runtime/Experimental/Chaos/Public/Chaos/PBDRigidClustering.h
GetClusterIdsArray The cluster ids provide a mapping from the rigid body index to its parent cluster id. The parent id might not be the active id, see the GetActiveClusterIndex to find the active cluster. INDEX_NONE represents a non-clustered body.
[TArrayCollectionArray](API\Runtime\Engine\Physics\Experimental\TArrayCollectionArray)< [ClusterId](API\Runtime\Chaos\Chaos\ClusterId) > & GetClusterIdsArray()